時效制度對2A97鋁鋰合金組織和力學性能的影響Effect of aging treatment on microstructure and mechanical properties of 2A97 Al-Li alloy

采用硬度測試、拉伸性能測試、DSC分析和透射電鏡(TEM)等方法研究不同時效制度對2A97鋁鋰合金組織和性能的影響。結果表明：采用165 ℃人工時效時，峰值強度最高，但其塑性也最差，且達到峰值的時間長達60 h；200 ℃人工時效時，達到峰值的時間縮短為6 h，而其峰值強度和塑性均很差；(200 ℃, 6 h)+(165 ℃, 6 h)雙級時效優(yōu)化后，可獲得比200 ℃峰時效更高的強度，其抗拉強度為545 MPa，只比165 ℃峰時效強度低11 MPa，伸長率卻提高至7.1%，且時效時間比165 ℃峰時效時縮短了48 h。2A97鋁鋰合金峰時效狀態(tài)下的析出相有T₁(Al₂CuLi)相、θ′相和一定量的σ(Al₅Cu₆Mg₂)相。根據(jù)不同升溫速率下的DSC曲線，采用Kissinger法求得T₁相的析出激活能為75.9 kJ/mol。綜合分析可知，采用(200 ℃, 6 h)+(165 ℃, 6 h)雙級時效可以得到比單級時效更加優(yōu)異的綜合性能。

The effect of aging treatment on the microstructure and mechanical properties of 2A97 Al-Li alloy during artificial aging was studied by hardness measurement, tensile test, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results indicate that 2A97 alloy obtains the highest strength, but its elongation is relatively low when aged at 165 ℃ for 60 h; when it is aged at 200 ℃, only 6 h is needed to achieve peak aging, whereas the peak strength and elongation are both poor; when the alloy is aged at (200 ℃, 6 h)+(165 ℃, 6 h), the aging time of which is 48 h less than that of single aging treatment when peak values are obtained, while the tensile strength is 545 MPa, only 11 MPa less than that of single aging treatment, and the elongation increases to 7.1%. The T₁(Al₂CuLi) phase, θ'''' phase and σ(Al₅Cu₆Mg₂) phase are the major precipitates in 2A97 alloy. According to the DSC curves at various heating rates, the activation energies of T₁ phases by Kissinger method is 75.9 kJ/mol. To sum up, the (200 ℃, 6 h)+(165 ℃, 6 h) double aging treatment can endow the alloy with more excellent comprehensive performance than single aging system.

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